Semiconductor light emitting devices such as light emitting diodes (LED) and laser diodes (LD) have been developed. In a semiconductor light emitting device, for instance, a nitride semiconductor layer of e.g. gallium nitride is crystal grown on a growth substrate. Here, if there is a large difference in thermal expansion coefficient between the growth substrate and the semiconductor layer, then after the crystal growth and return to room temperature, crystallinity degradation or cracks may occur and decrease the quality.